When the number of revolution of a clutch is used for engine control, it has conventionally been obtained by the detector of a pulse sensor, which detects shifting of tooth flanks of a ring-like pulse gear provided around a flywheel.
As shown in FIG. 4A, a sensor mounting mechanism 101 for a clutch case has been known, as an example, in which a pulse sensor 110 is inserted through a hole 103 into a clutch case 102, orienting a detector 111 of the pulse sensor 110 opposite to tooth flanks 100P1 of a pulse gear 100P. Numeral 112 refers to a support element for fixing the pulse sensor 110 to the clutch case 102 with a bolt 106 inserted in mounting hole 113 and numeral 104 refers to a boss formed inside the clutch case 102 for securely fixing the pulse sensor 110, respectively.
The conventional sensor mounting mechanism 101 for a clutch case has the problems described below.
Since the pulse sensor 110 contacts with the clutch case 102, there exists heat transfer between the clutch case 102 and the pulse sensor 110. The temperature of pulse sensor 110 will therefore rise, resulting in malfunction, when the clutch case 102 reaches high temperature.
The clutch case 102 manufactured by casting, which has a dead material 104a right under a boss 104 formed while the mold is extracted upward, inevitably weighs much. A mold which doesn't leave the dead material 104a requires complication, thereby resulting in an increase in manufacturing cost.
The adjustment of the clearance between the pulse sensor 110 and the detector 111 requires positioning of pulse sensor 110 by machining the clutch case 102, thereby involving a problem that mounting of the pulse sensor 110 inevitably becomes complicated, since the pulse sensor 110 is secured directly to the clutch case 102.